Posted
by
Soulskill
on Sunday April 29, 2012 @08:26AM
from the costly-mistakes dept.

Hugh Pickens writes "The Telegraph reports that although fly-by-wire technology has huge advantages, Airbus's 'brilliant' aircraft design may have contributed to one of the world's worst aviation disasters and the deaths of all 228 passengers onboard Air France Flight 447 from Rio de Janeiro to Paris. While there is no doubt that at least one of AF447's pilots made a fatal and sustained mistake, the errors committed by the pilot doing the flying were not corrected by his more experienced colleagues because they did not know he was behaving in a manner bound to induce a stall. The reason for that fatal lack of awareness lies partly in the design of the control stick – the 'side stick' – used in all Airbus cockpits. 'Most Airbus pilots I know love it because of the reliable automation that allows you to manage situations and not be so fatigued by the mechanics of flying,' says Stephen King of the British Airline Pilots' Association. But the fact that the second pilot's stick stays in neutral whatever there is input to the other is not a good thing. 'It's not immediately apparent to one pilot what the other may be doing with the control stick, unless he makes a big effort to look across to the other side of the flight deck, which is not easy. In any case, the side stick is held back for only a few seconds, so you have to see the action being taken.'"

and airliners.net also. The ones who know what they are talking about are unanimous in that it had little to do with the non-backdriven controls; the pilots flying were so disoriented that it probably would have taken a giant flashing sign saying "you're falling out of the air, dummies!" to get them to nose down.

And anyway, FBW != back-driven controls. The thread title is wrong and misleading. Boeing uses FBW too, but they back-drive the yoke and throttles. This has been discussed plenty as well, and there's no inherent advantage to one way over the other.

Yes and no –the reason they were ignoring the voice saying STALL, STALL, STALL was because they believed that the computer software made it impossible to stall the aircraft, and that all the warning meant was "if you turn off all the computer assistance now, it'll stall", not "the computer assistance is already all off, I am stalling".

A second warning that doesn't ever sound in safe scenarios (e.g. FALLING, FALLING, FALLING) might just have made them twig to "crap, it really is stalling".

No, they were never taught that Airbus aircraft will prevent a stall, no airline teaches that - what they did was assume the stall warning was incorrect, because they did not do their memory check lists as required by Airbus and Air France.

No, you're incorrect. There are various modes that the Airbus flight system uses. Under normal law, the airplane will not stall no matter what you do. You can pull up on the stick all you want, and the airplane will eventually gun the engines to avoid a stall. However, if the sensors are conflicting, the flight control software degrades into alternate law, which can be stalled. The flight crew might not have understood immediately that the alternative law mode had been engaged, and that a stall was probable. The entire episode took place in eight minutes with the captain being away, leaving two subordinates in charge.

That's one point against vi in the holy war with Emacs. System operating modes are distracting to humans. A state machine inside a state machine is loading short term memory too much in a critical situation.

No, that's not what happened at all. It's quite clear what happened. The one pilot was a fucking moron, and he had the stick pulled back the entire goddamn time they were stalled out and falling out of the sky. The other pilot had his stick pushed forward, trying to nose it down and gain some airspeed. The piece of shit computer system on the Airbus averaged the two inputs, finally concluding that keeping the control surfaces level was a good compromise. Only seconds before impact did the junior pilot (who

I only have 0.5 hours of recorded flight time, and even I know two important things that the people in that cockpit seemingly didn't:

1) Only one person can have control of the aircraft at once. When the captain says "my aircraft", the second in command takes his hands off the controls.

2) Pulling back on the stick makes a stall worse, not better. A stall is lack of airspeed. The solution for a stall is to increase airspeed. Either with the engines, or by pushing the stick forward, or both.

I thought the other part of this was also to let go of the stick as most planes have a tendency to right themselves if you just take your hands off the controls. I'm assuming the flaps and trim are setup okay, etc. But I'm not a pilot either.

You are referring to "positive stability", which is absolutely designed into the non fly-by-wire aircraft, such as the smaller Cessna's, Piper's, etc. With a fly-by-wire aircraft, the computers can handle the stability by making fine adjustments, leading the designers to make the aircraft closer to neutral stability. More the positively stable an aircraft is, the more aggressively it returns to a normal flight level, but you lose maneuverability. Commercial jets being closer to neutral stability, gives them more maneuverability, and slightly better fuel consumption.

Have you heard the claim that modern air force jets need X number of computers to stay in the air? This is due to them being designed with negative stability, meaning any pilot induced oscillation will grow larger and larger, therefor the computers are required to compensate for the lack of aerodynamic positive stability. The negative stability gives them a massive amount of maneuverability.

In any fly-by-wire aircraft, the computers will return the aircraft to a normal flight attitude. So the A330 has reduced aerodynamic postive stability (still above neutral), but the computer involvement makes up for this. Of course, when you lose the pitots, the computers drop from normal law to alternate law, which means they stop intervening in some situations, and instead warn the pilots. The prime example is a stall - you can't stall an A330 when running in normal law, as the computers will manipulate the control surfaces to prevent this. In alternate law, the computers are unsure of the full picture, due to failed inputs, so they warn the pilots of a stall. In this case, you have lost some of the stability introduced by the computers - there is some stability there, but when you are pulling back on the side stick while stalling in a storm, no amount of positive stability is going to correct it.

Positive stability doesn't fix all situations. If you have too low a power setting, out of trim, CG not correct or even strong external forces (such as a storm), the a positively stable aircraft can fail to stabilise itself.

Think of your car steering wheel. When you turn, it takes effort to move away from straight, and you feel continued pressure to return to straight. If you let go of the wheel, it will return to a straight position. This is positive stability. If your car had neutral stability, it would take much less effort (ie no resistance) to move away from the straight position, and if you let go of the wheel, it would stay in the turned position you left it in. If you had negative stability, turning the wheel would induce a force in the direction of your turn, encouraging and pulling the wheel further into the direction of turn. Letting go of the wheel would cause a turn to full lock. As you can imagine, this negative stability provides much more maneuverability, but requires computes to be able to bring the wheel back to central when the pilot indicates as such through the control column.

I have no flight time, no pilots license, never taken a lesson, never been in the cockpit of a plane, and have only been air-side in an airport when going on holiday.

From playing "Chocks Away" on the Acorn Archimides I can tell you that stick back = stall, stick forward = recovery. I'm not saying that I could recover from a stall in an actual aircraft; That's stupid. However, the principle is the same. Anyone who's flown any "flight sim" game could tell you this.

The BEA interim report will show you clearly when "dual input" situations happened. It's quite easy to follow, because there is an audible alarm each time that happens (the synthetic voice says "dual input"). You will see that even if there were a few moments of dual input, especially at the end of the stall when the pilots were panicking, overall this was quit short. The critical problem behind that crash is that nobody in the cockpit identified that the plane was stalling. In fact, nobody said the word "s

I've done a little researching on the A330's sensor system, and here is what I have found. Firstly, this article [wsj.com] describes pilot union concerns about the official report, and details some interesting facts about the stall warning system. Specifically, the stall warning system on the A330 sounded for 50 consecutive seconds before ceasing. This was apparently due to the computer system automatically turning off the warning once the plane had dropped below 70 miles per hour, since that speed was supposed to

When you introduce a paradigm where the computer does a bunch of the work automagically, there has to be a system that clearly and plainly tells the crew that the computer is not working normally anymore. There was such a mode on the Airbus but it wasn't really clear. For instance, if the stall warning turned off because you're going so slow the airplane believes the sensors must be wrong, the computer should tell you that instead of just turning the stall warning off and leading the crew to think that thin

The computer alerted them that the autopilot was disconnected almost immediately. They also in theory knew they were in alternate law. Why they did what they did? I'm guessing sleep deprivation and inexperience.

Perhaps you're not a pilot too, and if you go read the technical briefs about the crash you'll find that "STALL, STALL, STALL" can be issued by this aircraft even when the aircraft is not stalling, and has no possibility of stalling.

I am a pilot, and it is pretty obvious that the issue was that both of the young pilots just got behind the airplane. Just for the record, there is never a condition that a Stall horn should be ignored... These systems are always independent for good reason. The trainer aircrafts use a completely mechanical horn, and students must demonstrate several stalls to an FAA examiner (power on / power off) to obtain even a basic license. Meaning, there is no excuse for an airplane to stall other than pilot e

To paraphrase Churchill... Never in the history of aviation blogging has so much crap been said to so many by one who new so little.

Vacuum system on an A330? The only vacuum system on an A330 is the toilet.

The static system worked fine. They knew their altitude all the way to impact.

The pitot was heated. It was heated from the moment the first engine was started, automatically. The pitot design was unable to cope with the amount of supercooled water thrown at it. The subsequent design had problems, too. The current pitots by Goodrich work fine.

Nobody 'put their head in the sand.' They made a fundamental error at the start and then were deeply confused as to what their problem really was.

Seeing you expound an A330 crash based on your light aircraft experience is like watching a model rocketeer tell us what went wrong with Challenger based on his experience with cardboard tubes with fins.

The accident report is painful to read because it was so avoidable. Your post made me as angry as the accident made me sad because you don't know squat about jet aviation yet feel free to tell us exactly what went wrong.

From what I've read, the stall warning actually went away when the co-pilot pulled the nose up. I can't recall if that's because the pitot tubes were still messed up, or simply that the airspeed was too low that the stall warning only came back when speed was restored.

I read on pprune that this may have been avoided if there was angle of attack indication in the cockpit (plus training to use them). Apparently AoA is already measured by these aircraft, and such a reading would be much less ambiguous than gue

The airspeed dropped to a level where it was ambiguous (below something like 60 knots indicated), and that killed the stall warning. It reactivated when they pushed the nose down, which increased the airspeed to above the threshold.

The stall detectors base their alert on the amount of airflow and pressure on certain parts of the wing. At certain angles and speeds, there is either too much lift-like pressure generated(despite still being in a stall) or there is insufficient airflow to trigger the sensor, even to alert to the lack of airflow. More or less, it just assumes you aren't flying anymore since as far as the system can tell, there is no longer wind over the wing

Not only that, but the computer turned off the STALL warning when its sensors determined that it was going 60 knots in flight and decided it was wrong. It didn't tell the crew that it was shutting down the STALL warning due to sensor failure; it just stopped talking. When the co-pilot finally realized his mistake and began to nose down, the STALL warning turned back on again because the airplane had picked up speed. The co-pilot heard the STALL warning, freaked out, and began to pull up on the stick again. If he had kept nose down, the STALL warning would have gone away once the aircraft had sped up enough to get lift. It's a bizarre system all around.

The first rule is: don't freak out. If you feel like freaking out is OK, then don't be a fucking pilot, mmkay? Pilots who freak out die. It's a time proven observation.

A pilot who doesn't know that the AoA and airspeed are sourced by the same set of vulnerable sensors is silly. Next time when you walk down the jetway have a look on your left before you enter the plane. You'll see the pitot tubes sticking out. As an engineer, they'd be the first things I'd distrust if their outputs would be in disagreement with other sensors. Icing happens all the time, it's more common than uncommon.

Those pilots had perfectly good input from the inertial platform, GPS and perhaps radio altimeter. They should have looked at their fine instruments, determined what their ground track speed was, what the attitude was, and figured out what to do. End of story.

The stupidest thing was, the whole thing was avoidable. The reason they stalled out to begin with is the junior pilot decided to begin a long climb, for absolutely no reason, losing airspeed all the while. Then they got into the storm and couldn't see anything, as the aircraft began to stall. Junior pulled back on the stick and kept it pulled back hard until 5-10 seconds before impact.

They fell out of the sky for minutes on end while the other pilot had his stick pushed forward, desperately trying to nose it down and gain some airspeed, perplexed as to what the hell was going on and why the damn thing wouldn't respond.....as the computer system averaged the two inputs, giving a neutral control surface orientation. (What kind of fucking moron designs an aircraft control system like this?)

A few times Junior let up on his stick and the aircraft corrected enough for the stall warning to begin buzzing, then in terror he yanked it back again. Only at the very end did he finally let up and the aircraft began to recover, just as they belly flopped onto the ocean at 90 MPH.

I haven't listened to the transcript, but there's a procedure for taking over controls. Was there ever a "my plane" or "my controls" yell from the captain to the fo? Did the capt confirm that the other pilot had his hand off the stick? I mean, damnit, if you're experienced and shit goes wrong, you must presume that the other people are fucking up until you confirm for yourself that they aren't.

I concur, fly by wire-by-wire had nothing to do with it. Side sticks are here to stay and popular with more than just Airbus. A linked or back-driven yoke may have helped, but there's a far more compelling argument to be made for having Angle of Attack sensors and feedback.

If there was an Angle of Attack readout on the dash board that likely would have created a cross-check opportunity. The technology has been around for decade, but really hasn't caught on (or been required) commercially.

Indeed, the article is surprising, or more accurately, void of new informationBut there is another, worrying implication that the Telegraph can disclose for the first time: that the errors committed by the pilot doing the flying were not corrected by his more experienced colleagues because they did not know he was behaving in a manner bound to induce a stall. And the reason for that fatal lack of awareness lies partly in the design of the control stick – the “side stick” – used in all Airbus cockpits.
For the first time ? As you said, this has been beaten to death in various reports. There has already been an almost full transcript of the cockpit voice recorder leaked in a book [amazon.fr] months before. The last and final report from the investigators is scheduled to come out in June. They have put in place a special panel composed of pilots to try to understand the reactions of the crew (including seemingly ignoring the stall warnings, the apparent lack of confidence in the instruments, etc), and have dug into the history of flights during which pitots tube froze at high altitude. I think their conclusions might be slightly more revealing than the Telegraph copying-and-pasting other websites [popularmechanics.com].

I work in IT security. Looking good/bad (even yourself) is a purely secondary issue, if you take your work seriously.

That work is the reason, i read everything i can about airline incidents. Because their security practices are decades ahead of the one in IT (even with the occasional screwups). Their analyses are usually quite good too. But there is nothing a journalist cannot disfigure, once he sets his mind to it:-(.

When i read the annotated black box transcript a few weeks ago, i asked airplane experts about this. They told me:

If one pilot pulls and the other pushes the stick, there is an optical and audio signal.

Also the person was questioned if he pulls the stick and he confirmed it. Unluckily it was already too late by then.

I am no expert, but the root cause was IMHO the crew ressource management and training problem.

While I agree it was a CRM issue; the control system design contributed to this, IMHO. Just because there is a visual and auditory clue at some point does not mean that is understood and remembered; or that it was even heard on more than a subconscious level. Having a visual clue helps, so when you look at a control you see the actual order to the system, rather than a neutral position. That helps operators realize what the system is doing and will help them realize when something is not in a position they expect for a given situation.

Personally, I prefer Boeing's approach of having the controls positioned where they represent the input the system is receiving, that allows a pilot to scan the controls and develop an accurate mental model of what the plane is being told to do; which they can then determine if it is appropriate for the current situation. Not having that picture requires much more inquiry and analysis which may take critical seconds away from correcting the problem.

This is not a problem unique to the aviation industry; I've seen it happen in others where there are complicated systems that have a myriad of controls and require an good understanding of the current conditions to ensure operators respond correctly. Three Mile Island is a good example of a similar set of conditions that lead operators to make bad decisions that were compounded by the control system design.

Unfortunately, it is far easier to say "pilot or operator error" than fix the underlying causes that lead to that error when they are system control related.

Unaware of the real arguments, i would say: complexity. It would make a critical component more prone to problems.

Please be aware: The control stick in an Airbus is a small joystick today which is not in the "line of sight" of both pilots. You would have to look at it directly or put your hand there to notice it's position:

That arrangement of the sidesticks looks like a potential training problem. When a pilot is promoted to captain, he has to learn to operate the stick with the left hand instead of the right, and the throttle with the right instead of the left. For a pilot with thousands of hours flying, this has to be somewhat disorienting that requires a serious amount of training to overcome.

the thing with the Airbus control system is that you issue 'change' commands to the plane. you issue a 'roll command' when you push the stick to the side, and you issue a 'G command' when you push it forward or back. the plane will remain in the new commanded state until commanded otherwise.

(now read the last sentence again, and chew on it, make sure you understand it thoroughly)

thus, the usual way to fly the plane is to issue small, well-intentioned commands, not to pull on a stick for minutes, as one of the pilots here did. and the plane will stay in the new situation. 'will stay' means that it will issue corrections on its own to maintain the commanded attitude. for example, after having been issued a roll command for a few degrees, the plane will stay in that attitude even of there are disturbing factors - say, turbulence. (as a result, in such a case it is an error for a pilot to try to manually compensate for turbulence-induced attitude changes, as the plane does it on its own anyway, and he will end up over-compensating)

all-in-all, this is a big change in the philosophy on how to fly a plane, even when flying alone, when compared to a 'legacy' system of direct physical coupling of control instruments to control surfaces.

as for simultaneous inputs: actually, one of the pilots can 'take over' command of the plane, and shut out the other one, if he so chooses. none of the pilots did this on this occasion. when having multiple inputs, the plane does signal that the other person is entering inputs as well (at least visually, maybe there is also an aural indication). although, as pointed out, there is no physical feedback on the stick that would signal the other pilots inputs. when both are entering commands, their commands are 'added together'. thus a full pull & a full push on the stick will cancel each other out. two 'small' pushes will results a 'big' push. this makes sense, so that either pilot can 'adjust' the planes behaviour in addition to what is already happening.

the point of not having physical feedback is to reduce strain on the pilots. this way, the stick is always centered, and when moving off center, the pilot knows he's issuing commands to the plane. if it was not so, the pilot wouldn't be sure in which state of the stick is it in a 'neutral' position.

Issuing "small, well intentioned commands" is how it usually works, but in this case the flight controls had been switched into their alternate control law, due to the loss of reliable airspeed data. In alternate law the columns do what a "dumb" FBW system does, and stick displacement will reflect in contro surface deflection.

Only the pilot in command should have his hand on the stick; so linking the two together wouldn't have any of the problems you raise. It would, though, give valuable visual (and tactile if both pilots are trying to control the stick) information to the co-pilot.

this is not how multi-crew cockpits (MCC) work - in these cases, both pilots have control. as said earlier, they can agree on only one of them giving direct inputs though.

this is all covered by CRM - Crew Resource Management - where the two pilots divide the tasks & responsibilities between them. both being young pilots (remember, the captain was sleeping at the time), they pretty much failed in applying proper CRM techniques. both were used to being the junior member of a multi-crew cockpit, thus neither of them took the initiative. this is quite evident from the transcript.

There is one reason and one reason alone Airbus didn't link the sticks - and that's cost (both in higher building costs and extra weight).

this is simply not true - adding feedback is neither expensive nor heavy in this case.

There is one reason and one reason alone Airbus didn't link the sticks - and that's cost (both in higher building costs and extra weight).

>

The Airbus, like Boeings, have "Stick Shakers" to give feedback to the pilot. The stall waring indicator, in fact, does trigger the stick shaker, but once you get below a certain speed (like these pilots did) the aircraft thinks the plane is too slow to be flying so it must be taxing, so it turns it off.

while the co-pilots behaviour of pulling on the stick for minutes, and not recognizing the very simple stall-recovery process of pushing & gaining speed is, well, astonishing - there is a reason for his behaviour.

the reason is that such planes usually encounter stall-warnings on approach, when in a landing configuration, close to ground, and having a lot of excess power. in such occasions, the usual procedure is not to lower the nose & convert altitude to speed, but to simply 'power yourself out' of

in such occasions, the usual procedure is not to lower the nose & convert altitude to speed, but to simply 'power yourself out' of the stall situation - apply a lot of (available excess) power, and your speed will pick up, and you're not close to stalling anymore.

I'm not sure where you got that information, but that is not the correct course of action. Even in a low altitude situation, a stall can only be recovered by lowering the angle of attack... engine power and speed have absolutely nothing to do with it. A stall is an aerodynamic condition where the wings are not producing enough lift for flight. Pushing the nose over (to lower the angle of attack) allows the air to reattach to the wings which eliminates the stall condition.

Did the same person write the title and the summary of this story? Fly by wire has nothing to do with the control stick and everything to do with how the control inputs are sent to the control surfaces; some control schemes simply permit some cockpit/stick design decisions that in turn led to what the story is actually talking about... Though, you know, I think they should go back to lever & cable systems, then the pilot wouldn't be able to stall the aircraft because he'd never be able to exert enough force to pitch up.:P

It sounds like the problem here was that the plane was NOT in it's full fly-by-wire mode. The flight computer had given some control back to the pilots when it lost the pitots, and the pilots screwed it up.

Fly by wire means your electric inputs are converted into physical inputs by some other system. The two control sticks could be joined together, and the system would still be fly by wire if there was no mechanical link between the controls and the actual surfaces you are controlling.

I wondered why the pilots didn't respond to a stall by instinct. The feel of the plane should have been a major clue that something was wrong with their course of action. A lack of feel in the FBW system would certainly be a contributing factor in this kind of situation.

I wondered why the pilots didn't respond to a stall by instinct. The feel of the plane should have been a major clue that something was wrong with their course of action. A lack of feel in the FBW system would certainly be a contributing factor in this kind of situation.

The problem is your "feel" could be completely wrong when you lack visual clues and lead you to actions that worsen a situation. Pilots are trained to trust their instruments rather than what their body is telling them because of this.

It's the same reason why a motion simulator ride at an amusement park can be so convincing. You feel like you are flying but you are sitting right there. Tilting backwards feels very similar to forward acceleration. Flying in a controlled banked turn feels alot like sitting still.

As others noted, you can't always tell by feel alone, and they were flying in a storm at night, visibility sucked. Instruments and feedback on the controls are the best indicators in those conditions, and that plane doesn't give the same level of control feedback as others, so it all comes down to instrumentation.

They did get stall warnings, but only when they (briefly!) tried to put the nose down a bit, early on in the transcript. Pulling the nose back up, the stall warning went away - the plane's stall warning couldn't work at such low airspeeds or AoA (angle of attack).

So they had an alerting system that responded counter-intuitively. Pulling the nose up into a deeper stall actually made the stall warning go away. I've read on pprune that many pilots consider that if commercial airliners had AoA displayed in the

The problem described in the summary has nothing whatsoever to do with fly-by-wire. Yes, there may be an opportunity for improvement in that there should be some force feedback from one stick to the other. By that does not mean the plane can not be flown by wire. Plus, the fundamental issue in this accident is an operator mistake not corrected for by the other people present. I.e. it's a crew training & management issue.

Just in case this is a Boeing fan doing some Airbus bashing: Boeing is using fly by

The mechanical feedback facilitates a level of non-verbal communication. Assuming one seated pilot would know to push forward, he would at least feel - and that is much better than see that the pilot flying was not doing so.

Read it ALL on pprune (ignore the permanent troll there), and you'll see that things were quick, but not necessarily simple. The sad guy who just 'pulled' to misleading 1g stall had his young wife in the back, so don't ever think he wasn't trying. I do believe think the sidestick movement (lack of) and logic (deltaT, not proportional) is suboptimal, but that wasn't all.

Red herring #1: This isn't news.
--Maybe not to some of us. But TFA is new, and in a more general publication than the sources many of you have cited.

Red herring #2: This is an American anti-Airbus hit piece.
--Probably not. The Telegraph is a UK publication, and the title seems deliberately designed NOT to call out Airbus. See #3...

Red herring #3: The title blames FBW, that is a separate issue from back-driven controls.
--Quite right. Perhaps the author wished to avoid seeming anti-Airbus; perhaps he just wasn't precise in his phrasing. You sure don't have to read far to find out the truth.

Red herring #4: This is bullshit. The pilots fucked up.
--Perhaps you're not familiar with the English phrase "contributed to." It doesn't mean the same as "caused." In any safety-critical occupation, a piece of equipment that obscures the actions of one of the team members impedes the type of cross-checking that was a major reason for using a team in the first place.

No system is perfect. People are perfectly free to say that they think this is a minor issue which will only come up in very rare circumstances, more than compensated for by merits of the side-stick. Others might argue that the risks outweigh the benefits. I am smart enough to know that I am not qualified to have an opinion on the issue.

The problem with over-automation is that pilots may not know exactly what to do in case of an emergency, where decisions have to be made in split seconds. I mean, the entire crash took eight minutes to unfold. The Airbus paradigm keeps the pilot out of the loop to minimize fatigue. The crew is used to computers doing all the nitty-gritty stuff. However, when there's a stall warning, it takes way too long for them to realize what's going on.

Apparently, it's not possible, or practical to just look and see what the driver is doing. It takes

a big effort to look across to the other side of the flight deck, which is not easy

Now, it's a long time since I've been on a flight deck, but they weren't that big. What's changed so much that it's such a huge imposition for someone to look at the guy in the other seat and see "oh yes, he's pulling back on the stick" and then maybe slap him around the head until he stops.

in my opinion the biggest issue was that the pilots weren't aware of the huge angle of attack (AOA) that they were maintaining, and AFAIK they didn't have an AOA indicator in the cockpit. it was also dark and in a big storm, thus there were no external references.

they had the plane pitched up about 10 degrees, which is not that big. they also had speed - they were close, but not below stall speed. but at the same time they were falling badly, which meant their angle of attack on the wing leading edge was at least 30 degrees if not more.

remember that the basic reason of a stall is always high AOA - not speed, not pitch, but high AOA.

of course, you 'should' be able to put it together - high pitch, large negative vertical speed -> high AOA. it seems the young co-pilot didn't.:(

Last year I watched a special on a TV network about this tragedy. I can't remember if it was History, Science, etc. But they had shown that there was a very good chance that all of the speed sensors on the plane had frozen over with ice. Those speed sensors are critical to the operation of a fly by wire plane regardless if it's being flown manually or by auto pilot.

I'll try to find the video or transcript because it was a very well thought out scenario of what likely happened. The experts on the show sa

yes, this was how the whole thing started - that they got an incorrect airspeed indication, and thus the autopilot disengaged. after a short while, the speed indication was correct again. unfortunately, human errors added up starting from there.

although I would argue that the first mistake that they made was to fly into the storm, which every one else navigated around at that time. in aviation, you have to have at least 3 mistakes in a row to have an accident - here, flying into the storm, the frozen airspace indicator and then human error.

This is more of a loss of instrument data problem. The pilots (and the computers) did not have reliable altitude, airspeed, or vertical speed information. They were in a storm at night. Read the third interim report [bea.aero], which has the data from the flight recorders. See section 1.16.6, "Reconstruction of information available to the crew".

Bear in mind that this event started with loss of airspeed information: "The PF then said âoeWe haven't got good... We haven't got a good display...of speed"
and the PNF "We've lost the speeds"." This was due to pitot tube icing. From the voice recorder information, it appears that the pilots never again trusted the airspeed information presented. The speed data did come back for a while, but then was lost again.

The aircraft was then in a high altitude stall:
The airplane's parameters were then: altitude about 35,800 ft, vertical
speed -9,100 ft/min, computed speed 100 kt and falling, pitch attitude 12 deg. and engine N1 for
both engines at 102%. But one of the pilots said At 2 h 12 min 04, the PF said that he thought that they were in an overspeed situation,
perhaps because a strong aerodynamic noise dominated in the cockpit.
The report says "Despite several references to the altitude, which was falling, none of the three crew members seemed to be able to determine which information to rely on: for them, the pitch attitude, roll
and thrust values could seem inconsistent with the vertical speed and altitude values."

Again, this is in a storm, at night, over ocean. All the crew has is its instruments. The crew misjudged which data was correct and which was wrong. Still, they had several minutes, three pilots, and plenty of airspace and altitude to deal with the problem. There was a way out. If the initial events had happened over high mountains, there would have been far less time to deal with the situation.

There are fighters which are designed unstable for maneuverability and can't fly at all if they lose their air data inputs. They have ejection seats. Transport aircraft are more stable and can manually flown without air data inputs, but it's not easy. A technical argument here is that aircraft with computer-assisted flight controls should have much more redundancy in the basic air data inputs (altitude and airspeed). If the sensors had worked, the computers would have prevented this. The Airbus had three pitot probes, but they were all the same, and vulnerable to icing. It may be appropriate to require some completely different sensors, mounted on different parts of the aircraft, as a backup.

Much of the blame belongs to Thales, which built the pitot probes. There were known problems with those probes before this crash. Air France has since replaced all Thales probes with Goodrich probes.

If the crew had diagnosed the situation as a failed pitot tube, all they had to do was to turn the throttle to 85% power, and point the nose up 5 degrees and everything would have been fine. The computer was not providing the angle of attack information to the crew, nor was it giving any indication of the throttle setting. Therefore, there was no way to make see that proper steps were not being followed.

I find the half-assed approach when it comes to automation disconcerting. Either let the computers fly it and the humans are simply there as adjuncts and baby sitters, or let the humans fly it and the computer just corrects for fuck-ups. But in this case it was bunk information that confused even the computer. Blacking out screens is sort of a half-assed way to go about telling the world you're confused.

And why is it they still use Pitot tubes when GPS has fairly high resolution in three dimensions?

What did Chernobyl, Three Mile Island and the Space Shuttle Challenger have in common?

All three disasters were due to erroneous decisions made by (otherwise) smart, trained people at the wee hours of the morning. This has been shown to be have a bad effect on human decision making,

So the first thing I noticed was the fact that this disaster happened at 2am (not sure what time zone it was in or what time zone the pilots were in but you get the point).

Obviously someone has to be awake at all times to fly a plane (or operate a nuclear plant) but perhaps they could've timed the captain's rest better and made it clearer who was in charge when he was asleep.

The thing that always amuses (yet frustrates) me is that the Luddites weren't against technology, they were against workers being replaced by machines. If the mills had kept the same workforce but doubled production, diversified, or whatever, they wouldn't have complained.

A true Luddite would not complain about fly-by-wire as it's not replacing anyone. They'd applaud it because it was enhancing the skills of the people who were there.

First, I fail to see the relationship between joysticks and tactile feedback, secondly it's very possible and often done for fly by wire systems to provide force feedback and other haptic ques. The failure is with the designers of the system who opted to omit such feedback, not intrinsic to fly by wire.

Every component in the system introduces the possibility of error, agreed.People can detect and correct certain classes of error better than machines, but machines can detect and correct certain classes of error better than people.People can self-repair, to an extent. Blake's 7 Liberator-style auto-repair is still sci-fi. Sadly.Well-trained humans can identify errors in their training but can also forget the training that is correct. Computers cannot (yet) do either.